This invention relates in general to membrane separators and to fuel processing systems.
In the field of hydrocarbon fuel processing, a need exists for efficient ways to reduce organic sulfur components and other contaminants. An example of the need for new desulfurization approaches involves power generation. One promising technology is fuel cells, which can provide a silent source of power having a low heat signature. However, most fuel cells require hydrogen or a hydrogen-rich gaseous mixture as fuel. Short of providing stored hydrogen gas, the primary means of supplying hydrogen is by reforming a hydrocarbon fuel. Both liquid and gaseous fuels may be reformed, with liquid fuels typically being more difficult due to more complex molecules and contained contaminants.
The fuel input to a liquid fueled fuel cell system must generally be free of specific contaminants, the most problematic being sulfur. However, liquid hydrocarbon fuels generally contain sulfur levels that are too high for direct use in fuel cells. For example, typical military and aviation fuel specifications allow up to 3000 ppm in JP8, JP5, and Jet-A. These are all common aircraft fuels, the first two being exclusively military fuels. Gasoline, diesel and heating fuels in the US have lower sulfur limits (15 ppmw), but the allowed and typical sulfur levels are still above those acceptable to fuel cell systems including most reforming technologies.
Current technologies for removing sulfur from liquid hydrocarbon feedstocks include hydrodesulfurization (HDS), a technology well known in the commercial world. Most commonly, HDS is carried out with hydrogen gas at high pressure being passed over a liquid hydrocarbon fuel in a cascade or trickle bed reactor. In a separate invention, Battelle Memorial Institute has developed an HDS system wherein a hydrogen-containing gaseous mixture, with the hydrogen at high partial pressure, is mixed with vaporized raw fuel and put in contact with a selective catalyst (see U.S. patent application No. 2009/0035622 A1, published Feb. 5, 2009, which is incorporated by reference herein). In both systems, the sulfur in the fuel then combines with the hydrogen, freeing itself from the fuel and becoming primarily gaseous hydrogen sulfide. The hydrogen sulfide can then be absorbed or removed by other means.
There is a need for an improved apparatus for supplying hydrogen at high pressure for use in HDS systems and other applications. There is also a need for improved fuel processing systems including such an apparatus. More generally, there is a need for an improved apparatus for supplying pressurized gases for many different applications.